1 2. Program Construction in Java

2.00 Programming Fundamentals

3 Topic 2 Part 0??????? Get used to it. Computer scientists start counting at zero.

4 What is a program? A list of instructions telling the computer what to do. It must be precise and its semantics and syntax, (logic and grammar/spelling) must be correct if translation into machine code is to succeed.

5 Why Java? Java has these advantages over other languages: ‣ it is a high-level programming language (closer to human language than machine code); ‣ it is event-driven (it can respond to user mouse clicks and key presses);

6 Why Java? ‣ programs can come as two types: applications (run on their own) and applets (run in a web browser, making Java very web user-friendly); ‣ executables in other languages have too much access to the system and can't be trusted - the sandboxing in Java means it is difficult to write a virus or crash the whole system;

7 Why Java? ‣ it is effectively a platform in itself and so is platform-independent (programs will run on Windows, Macs, Linux, etc.) - the Java compiler actually creates byte code which is standard and will be converted to the machine's native machine code at run time;

8 Why Java? ‣ it is simpler than other languages, so easier to learn, so fewer bugs and bugs are easier to spot; ‣ it is object-oriented which makes it easier to conceive and work with GUI (window- based) interfaces;

9 Why Java? ‣ it is multithreaded, meaning programs can run several tasks simultaneously, (as can Windows of course), unlike older style procedural programs; ‣ the different files (classes) of a Java project are independent but dynamically linked so they can use each other automatically when required;

10 Why Java? ‣ memory allocation is more efficient than in other languages (Java uses what is called garbage collection to liberate memory that is no longer needed); and ‣ the IBO says we must!

11 Java’s reserved words Some words, called keywords, e.g. class, true are reserved by Java. This means you cannot use them for your own purposes e.g as a variable name.

12 Pseudocode An artificial simplified programming ‘language’ used to describe algorithms without using the rules of any particular programming language. During the development of an algorithm, pseudocode often contains sections of natural language that will be replaced later.